Polylactic acid resin is expected as a practically excellent biodegradable polymer because it has a high melting point and is melt-moldable. It is a thermoplastic resin with low environmental load that is also expected to be used as a general-purpose polymer prepared from biomass materials in the future and has been increasingly used as a molded article by molding such as injection molding and extrusion molding. However, in application of a polylactic acid resin, for example, to electrical and electronic equipment parts and office automation equipment parts, it has been necessary to highly improve particularly flame retardancy as well as molding processability, shock resistance, and heat resistance.
For example, Patent Document 1 discloses, as a method for improving the flame retardancy of a thermoplastic resin, the invention that highly improves flame retardancy by adding a phosphate compound and a phosphate ester compound with a particular structure to a synthetic resin. Patent Document 2 discloses a flame retardant composition obtained by adding silicone oil with a particular viscosity to a flame retardant composition composed of a salt of piperazine and an inorganic phosphorus compound and a salt of melamine and an inorganic phosphorus compound and a flame retardant polyolefin resin composition. Further, Patent Document 3 discloses a flame retardant composition obtained by adding silicone oil, a monoamide compound, and/or a monoester compound to a flame retardant composition composed of a salt of piperazine and an inorganic phosphorus compound and a salt of melamine and an inorganic phosphorus compound and a flame retardant synthetic resin composition.    Patent Document 4 discloses a polylactic acid resin composition containing a polylactic acid resin, a particular plasticizer, a particular crystal nucleating agent, and a phosphorus flame retardant other than phenyl phosphonic acid metal salt and discloses phosphate and condensed phosphate as a phosphorus flame retardant.